EP1591704B1 - Vehicle with gaseous fuel and automatic purge system - Google Patents

Abstract

The road vehicle includes a gas tank (2) connected to at least one vent channel (3) through a normally closed thermal release valve (5) such that the vent channel leads to a discharge orifice. The thermal release valve can be opened spontaneously under the effect of a temperature rise. The thermal release valve is installed in a predefined zone remote from the discharge orifice. An independent claim is also included for a valve for gas tank of road vehicle.

Description

FIELD OF THE INVENTION

The present invention relates to gas storage tanks in a road vehicle regardless of its engine, and in particular but not only applicable for the storage of hydrogen gas and / or storage of oxygen gas in a fuel cell vehicle .

STATE OF THE ART

One of the problems of storing gas on a vehicle is the danger in the event of a fire occurring in the vicinity of the tank, as well as in the event of too high a rise in pressure. It has already been proposed for the liquefied petroleum gas vehicles discharge valves to allow the gas to leak gradually in case of overpressure, caused for example by abnormal heating due to a fire, because it is necessary at all costs to avoid the risk of explosion, even if the fuel is fueling a fire at a limited flow rate. Thus, safety valves that are irreversibly open under the effect of a warm-up have already been proposed in the state of the art: the reader can consult for example the request JP60 / 073200 which describes such a safety valve in which the sealing element is a diaphragm closing an orifice and the element controlling a definitive opening is a pellet made of shape memory alloy carrying a needle, so that, in the case of When heated, the shape-memory alloy chip changes shape and pushes the needle against the diaphragm until the diaphragm breaks.

However, there is no known solution robust enough to find a location in an automobile and play a role of safety only in case of fire, and play certainly in case of fire. Thus, for example, there is no satisfactory solution to prevent the gaseous fuel escaping from the tank aggravates a fire that could have occurred without the fuel system being at the origin. Thus, in the event of an accident involving several vehicles, if one of these vehicles loses its fuel which then spreads on the roadway, for example gasoline, there is a significant risk that the gasoline ignites and that another vehicle is immobilized over this fire. In this case, if the fire takes place under the fuel tank of a gaseous fuel of that other vehicle, assuming that it is equipped with a relief valve in case of overpressure, it is first necessary to wait until the pressure in the tank rises before such safety plays its role. In addition, if the pressure in the tank is low because the residual amount of fuel is low, it will take longer before such safety acts, so much so that the constituent material of the tank may have lost its mechanical properties to the point of yielding and thus causing an explosion even before the pressure is high enough for the overpressure relief valve to act.

If it were possible to act sooner to purge the tank, the safety conditions of vehicles storing a gaseous fuel under pressure, such as fuel cell vehicles powered by hydrogen, would be improved.

In the field of fuel cell vehicles, the patent application WO03 / 035419 proposes means for evacuating hydrogen not consumed by the cell, collecting leaks around the cell, collecting leaks around the tank and installing a pressure relief valve on said tank. Again, nothing is planned to improve safety in case of fire.

The document EP 1070620 discloses a vehicle according to the preamble of claim 1, and a thermal trip safety valve.

BRIEF DESCRIPTION OF THE INVENTION

An object of the invention is to ensure that, in the event of a fire, the tank of pressurized fluid existing on board a vehicle is automatically purged as quickly as possible, taking the fluid as far as possible. possible from where the fire broke out.

This object is achieved according to the invention by means of a vehicle as defined in claim 1, or a valve as defined in claim 9.

The invention proposes a vehicle equipped with a reservoir for storing a fluid under pressure, said reservoir being connected to at least one purge line, said purge line ending in at least one discharge orifice, the purge line being connected to the tank by means of at least one safety valve, characterized in that the safety valve is a normally-closed thermal release valve capable of opening spontaneously under the effect of a rise in temperature , the safety valve being installed in a predefined area of the vehicle and the discharge port being remote from said predefined zone.

The invention also proposes a thermal release valve comprising a triggering mechanism using a triggering element made in a shape memory alloy of characteristics such that, when it is subjected for the first time to a rise in temperature leading to Beyond a predefined temperature threshold, it adopts a memorized form and adopts it in a thermally irreversible way.

Two practical embodiments of an application to a hydrogen reservoir are described below.

The first embodiment uses a safety valve comprising an opening mechanism controlled by a chip made of shape memory material. The other embodiment provides a safety valve controlled by a mechanism comprising a capsule destroyed by the effect of heat. In both cases, the two embodiments have the advantage that they work even when the electrical installation controlling the entire operation of the vehicle is out of service. Indeed, the elements necessary for the control of the safety valves operate on thermomechanical principles.

For example, the tank itself can be installed at the rear of the vehicle. It can also be installed especially in the floor, in the central part of it because it is an area unlikely to be deformed even in case of particularly violent accident of the vehicle. It is possible to route the pipe for conveying the fluid under pressure out of the vehicle by passing through a zone that is particularly sensitive to the risk of fire and to install the safety valve there.

For example, noting that there is a risk of a fire under the floor of a vehicle, the bleed line may run under the floor to install a thermal release valve at that location, and then the bleed line continues to the discharge port which is disposed away from the floor, for example on the roof of the vehicle. It is this application which is illustrated in more detail below.

But there are many other possible applications. If it is considered that the consequences of a fire occurring in the engine compartment must be guarded against, the pipe may also be installed so as to reach the front of the vehicle, for example in the compartment where the battery is located. fuel producing the electrical energy necessary for the vehicle, so as to install the thermal release valve, then the purge pipe runs to the discharge port which is disposed far from this compartment, for example at the rear of the vehicle. We can treat in the same way several areas where we consider that there is a significant risk of beginning of fire and of which we want to cancel or at least reduce the consequences. For example, the passenger compartment of a vehicle can be treated. The tank can be treated with any dangerous gas, including all gases mentioned above.

Finally, it should be added that several purge lines can be installed in parallel, all of them from the same tank, all leading to the same discharge port, each passing through a vehicle zone where a fire is likely to take place, to install a thermal release valve.

A nonlimiting example of use of the invention is illustrated below in the case where the reservoir is of a particular type, described in the patent application. EP 03 / 028056.4 filed on December 8, 2003.

BRIEF DESCRIPTION OF THE FIGURES

• La figure 1 est une vue d'un véhicule de tourisme montrant l'implantation générale des organes de l'invention ;
• La figure 2 montre une soupape de sécurité en configuration normalement fermée, associée à un réservoir à cellules multiples ;
• La figure 3 montre la même soupape de sécurité que celle de la figure 2, cette fois en configuration ouverte ;
• La figure 4 montre une autre soupape de sécurité en configuration normalement fermée, associée au même réservoir à cellules multiples ;
• La figure 5 montre encore une autre soupape de sécurité en configuration normalement fermée, toujours associée au même réservoir.

In the following figures:

• The figure 1 is a view of a passenger vehicle showing the general location of the organs of the invention;
• The figure 2 shows a normally closed configuration safety valve associated with a multi-cell reservoir;
• The figure 3 shows the same safety valve as that of the figure 2 , this time in open configuration;
• The figure 4 shows another normally closed configuration safety valve associated with the same multi-cell reservoir;
• The figure 5 shows yet another safety valve in normally closed configuration, always associated with the same tank.

DESCRIPTION OF THE BEST MODE OF REALIZING THE INVENTION

To the figure 1 , we see a passenger vehicle having a floor 10 incorporating at least one tank 2 for storing on the vehicle a gas under pressure. It can be any fluid stored at high pressure, for example liquefied petroleum gas, compressed natural gas or compressed hydrogen, or oxygen. In the following, it is assumed that the tank 2 is a storage tank for a single gaseous fluid, for example hydrogen gas, without this being limiting.

To the figures 2 and following, we see that the reservoir 2 has a very large number of cells 20 small volume, interconnected. The reservoir comprises a base 21 which has as many recesses as cells 20. The recesses all extend from a first face 22 to the opposite face 23. They are all opening to the first face 22 and not opening to the opposite face 23. Each recess is closed by a plug 24, except where a safety valve is installed which then takes the place of such a plug. The plugs 24 are screwed on the base 21, a seal 24A being provided in a suitable groove. For more details on the constitution of tank 2, the reader is invited to refer to the patent application EP 03 / 028056.4 supra.

A protective plate 25 is pressed against the lower face 23 of the tank 2. A collection pipe 3 is disposed just below the protective plate 25, longitudinally with respect to the vehicle. This collection pipe 3 is here of very flattened rectangular section, which also appears in the following figures. On the front side of the vehicle, this collection pipe 3 is closed off by a wall 31. On the rear side of the vehicle, the collection pipe 3 leads to one or two joints 32 to which pipes 33 are coupled. The collection pipe 3 and the pipes 33 together form the purge pipe. The pipes 33 join discharge ports 34. These are located on the rear vertical wall 11 of the vehicle 1, at a level close to the roof 12.

The collection pipe 3 comprises a number of first holes 30 (see figure 2 ) made at least on one of the large faces of the collection pipe 3. Furthermore, the collection pipe 3 comprises a number of second holes 30B made on the other of the large faces of the collection pipe and facing each of The first holes 30 and the second holes 30B are for example made in five places as seen in the figure 1 . The first and second holes 30 and 30B are exactly opposite five cells 20 of the tank 2. The protective plate 25 also has five holes, also exactly opposite the same five cells 20 of the tank 2.

Safety valves are screwed on the tank 2, instead of as many plugs 24 as already mentioned, that is to say in relation to the five locations mentioned above. The collection pipe 3 is kept pressed against the protective plate 25 and thus against the tank 2 so as to ensure communication with the safety valves and the sealing with respect to the outside. In this example, three thermal trigger valves 5 and two pressure threshold valves 6 have been used, the structure of each of these valve types being detailed below. Thus, the collection pipe 3 allows the parallel connection of several cells 20 and, when one or more of the safety valves installed on some cells 20 open, the gaseous fluid that escapes through the Safety valves are collected by the purge line and discharged to one or more discharge ports 34.

Let us now turn to the construction details of a thermal tripping safety valve 5. A first variant embodiment is illustrated in FIGS. figures 2 and 3 .

We see a body 50 having a thread 51 to be screwed on the tank 2. This body 50 has a seat 52 closed by a ball 53. A spring 59 can be installed which causes a moderate preload tending to push the ball 53 against its seat 52. Furthermore, the higher the pressure of the fluid inside the cell 20, the more the ball 53 tends to press firmly against its seat 52, thus ensuring a perfect seal.

Beneath the seat 52 is a chamber 54 communicating with conduits 55 terminating on the side wall of the body 50. The center of the body 50 has a bore inside which is mounted a sleeve 56 for guiding a central piston 57. On the opposite side to the seat 52, the body 50 comprises a collar 58 receiving by screwing a shutter 70. The shutter has on one side a central cylindrical wall 73 and a peripheral ring 72. On the inside, the shutter 70 traps a pellet 7 made of shape memory alloy, which is also supported on a ring 71, itself mounted against the body 50. Note that when the body 50 has been screwed on the tank 2, the body 50 overflows tank 2. Thanks to the first 30 and second 30B holes made on the collection pipe 3, and through similar holes made on the protective plate 25, when one installs said protective plate and the collection pipe, the flange 58 of each of the bodies 50 remains accessible from the outside. The shutter 70 can be screwed onto the body 50 while trapping the protective plate 25 and the collection pipe 3 thanks to the ring 72 of each shutter 70, said ring pressing on the outer wall of the collection pipe 3. The collection pipe 3 is thus held tightly on the body 50.

The figures 2 and 3 show a shutter 70 of the blind type, that is to say it has a thin central cylindrical wall 73, to isolate the pellet 7 from the outside. This has the advantage of offering mechanical protection against external aggression, without significantly delaying the heating of the pellet 7. But it is also possible to consider using a fastener devoid of this thin central cylindrical wall, which allows direct contact of the heat source (flames) with the pellet 7, for a minimum reaction time.

The valve proposed by the invention may be useful in applications other than the passenger vehicle 1 described above. It is of permanent opening type as soon as it is subjected to a first rise in temperature. It comprises a ball cooperating with a seat and a spring pushing the ball against its seat to maintain the valve in the normally closed position at room temperature, and comprises a memory shape memory chip having a first form at ambient temperature, a piston being interposed between the ball and the pellet. According to an essential characteristic of the valve according to the invention, the shape-memory alloy chip is of a type that adopts a memorized shape the first time it is subjected to a rise in temperature. As a result, the piston pushes the ball out of its seat when the pellet passes from the first shape to the stored shape.

Shape-memory alloys are known to transform from one crystalline structure to another during passage through a defined temperature zone. It is from this transformation that shape memory alloys have their properties and their denomination. As a result, any object made of shape memory alloy can be given two different forms: one at low temperature and the other at high temperature, hereinafter called "memorized shape". The temperature zone at which the transformation occurs depends on the composition of this alloy and the education that is subjected to this alloy by exerting certain mechanical stresses under determined temperature conditions.

This being recalled, with regard to the production of the pellet 7, use is made, for example, of a shape memory metal NiTi. This alloy undergoes a change of its crystalline structure when it is cooled, that is to say that it passes from its hard state, of austenitic structure (high temperature), to its easily deformable state, of martensitic structure (low temperature) . The chosen transition temperature for the pellet 7 is about 90 ° C (at + or - 5 ° C). A material having the required properties is well known to those skilled in the art; for information, it is available for example from Special Metals Corporation, New Hartford, NY. The pellet has as initial shape a spherical cap (close to that shown in FIG. figure 3 ). At room temperature, the pellet is in the Martensite (soft) state. It can be quite easily mechanically deformed so as to reach an approximately flat shape (disk shape, illustrated in FIG. figure 2 ). When the pellet reaches a temperature of the order of 90 ° C, it changes phase and passes from the Martensite state to Austenite (hard) state. It thus returns to its initial form (memorized form) which is a spherical cap. This form persists even after a return to room temperature. This means that the chosen material is irreversible in its shape while being reversible in its structure because it has gone from the Austenite (hard) state to the Martensite (soft) state. The only way to get him back to a disc shape is an external mechanical action.

Preferably, in the normally closed position at room temperature, there remains a slight clearance between the pellet 7, the central piston 57 and the ball 53, so that it remains firmly pressed against its seat 52. figure 2 , we see the pace of the pellet 7 at room temperature.

To the figure 3 , we see the pace that takes the same pellet 7 under the effect of a rise in temperature (stored form). The degree of deformation depends on the size of the pellet 7 itself. For a pellet made as indicated above, the deformation begins when the pellet 7 has reached the temperature of 75 ° C. As soon as the editing games are caught, the pellet develops a major effort. As soon as the ball has been raised sufficiently, the force developed by the pellet decreases but remains sufficient to combat the force developed by the spring. Maximum deformation is achieved as shown in FIG. figure 3 when the pellet 7 has reached the temperature of 100 ° C. In addition, it turns out that such a pellet 7 is capable of developing a sufficiently large force to be able to push the piston 57 against the internal pressure which applies to the ball on the side of the cell containing the high pressure fluid ( of the order of 200 to 300 bar), and against the pressure of a holding spring.

As already indicated, after thermal stress and cooling of such a pellet 7, if it was desired to make it resume its original shape, for example to repackage the thermal tripping safety valve 5, it is necessary to deform it mechanically. Thanks to the pellet 7, the fact that a sufficient heating makes it permanently take said stored form, the valve 5 opens reliably and remains open even if the heating decreases or ceases.

It has just been indicated that the thermal tripping valve 5 comprises a pellet 7 made of shape memory alloy. This is a preferred embodiment of a trigger mechanism using a trigger member made of a shape memory alloy, said shape memory alloy being of such characteristics that it adopts, when subjected to a first time at a temperature rise bringing it beyond a predefined temperature threshold, a memorized form, and this in a thermally irreversible manner.

Of course, a number of seals are used to ensure perfect tightness of the assembly, as is clear from the drawings without further explanation. The ducts 55 leading to the side wall of the body 50 are in direct communication with the collection duct 3 so that, when the thermal tripping safety valve 5 is opened, the gases escape into the chamber 54 and then walk through the ducts 55 leading to the side wall of the body 50, where they join the collection pipe 3, without being able to escape into the external environment at the thermal tripping safety valve 5 of the collection pipe 3.

Of course, other types of valves can be added, such as a pressure threshold valve 6 such as that illustrated in FIG. figure 5 . This uses the same body 50 as the body of the thermal tripping valve 5. On the tank side, this body 50 receives an insert 63 having in its center 630 a calibrated rupture membrane. The insert 63 is interchangeable. The chamber 54 is closed by a cap 67. The body 50 receives a nut a shutter 70 blind type identical to that used in the figures 1 and 2 .

Thus, in a particularly advantageous embodiment of the invention, the vehicle tank comprises a set of interconnected cells to ensure the circulation of fluid necessary for the use of the vehicle, at least two cells each being connected to the purge pipe. , each of the cells being connected to the purge line by means of least one safety valve, one of the safety valves being said thermal release valve, the other of the safety valves being a pressure threshold valve opening automatically and permanently (irreversible opening for example by destruction of a operculum) beyond a predefined pressure threshold.

To the figure 4 , there is shown an alternative embodiment of a thermal release valve 8, wherein the triggering mechanism uses a capsule destructible under the effect of heat (not used in the figure 1 ). We see a body 80 having a thread 81 to be screwed on the reservoir 2. This body 80 comprises a first bore 82 closed by a central piston 83 having a head 88 and a skirt 880 defining a hollow central zone open on one side and closed on the other side by the head 88. The body comprises a central chimney 86 defining a second bore 84 having a diameter slightly greater than the diameter of the first bore 82. The central piston 83 is guided in the second bore 84. The interior the central chimney 86 communicates with one or more conduits 85 terminating on the outer wall of the chimney 86. The chimney 86 is closed by a shutter 87. A capsule 89 is interposed between the shutter 87 and a bearing washer 90 deposited against the head 88 of the piston 83. This capsule 89 breaks at a preset temperature. For example, such breakable capsules can be found at a temperature of the order of 90 ° C at JOB GmbH, Kurt-Fischer-Strasse 30, D-22926 Ahrensburg.

The body 80 further comprises a third bore 91 inside which is mounted a sheath 92 defining a substantially annular space around the chimney 86. This space is in communication with the collection pipe 3. When the capsule 89 breaks, more nothing prevents the central piston 83, on which the pressure of the fluid in the cell 20, to move back against the shutter 87, thus putting the cell 20 in connection with the inside of the chimney 86, with the conduit or ducts 85, with the substantially annular space surrounding the chimney, and finally with the collection pipe 3.

Various seals ensure perfect tightness of the assembly, as shown in the drawing without the need for further explanation. Apart from the central trigger mechanism, the valve of the figure 4 is quite similar to that of figures 2 and 3 , its purpose being in any case identical.

Claims (10)

1. Vehicle (1) equipped with a tank (2) for the on-vehicle storage of a pressurized fluid, the said tank being connected to at least one purge line (3 and 33), the said purge line leading to a discharge orifice (34), the purge line being connected to the tank by means of at least one thermally triggered safety valve (5) that is normally closed and is capable of opening spontaneously under the effect of an increase in temperature, characterized in that the safety valve comprises a triggering mechanism that uses a triggering member made of a shape memory alloy of characteristics such that, when subjected for a first time to an increase in temperature that raises it beyond a predefined temperature threshold, it adopts a memorized shape and adopts it thermally and irreversibly, the safety valve being installed in a predefined region of the vehicle and the discharge orifice being distant from the said predefined region.
2. Vehicle according to Claim 1, in which the thermally triggered valve (5) is adjacent to the tank (2).
3. Vehicle according to Claim 1 or 2, in which the discharge orifice (34) is situated on the vehicle in a region as far away from the thermally triggered valve (5) as possible.
4. Vehicle according to Claim 1, in which the thermally triggered valve (5) comprises a ball (53) cooperating with a seat (52) and a spring (59) pushing the ball back against its seat, and in which the triggering mechanism comprises a shape memory alloy pellet (7) that has a first shape at ambient temperature, a piston (57) being inserted between the ball (53) and the pellet (7), the shape memory alloy pellet being of the type that adopts a memorized shape, different from the first shape, as soon as it is subjected for a first time to an increase in temperature, the piston pushing the ball away from its seat when the pellet switches from the first shape to the memorized shape.
5. Vehicle according to one of Claims 1 to 4, in which the tank comprises a collection of cells (20) that are interconnected so as to allow the fluid needed for use of the vehicle to flow.
6. Vehicle according to Claim 5, in which at least two cells (20) are each connected to the said purge line, each of the cells being connected to the purge line by means of at least two safety valves, one of the safety valves being the said thermally triggered valve (5), the other of the safety valves being a valve (6) with a pressure threshold that opens automatically when a predefined pressure threshold is crossed.
7. Vehicle according to one of Claims 1 to 6, comprising a floor, in which the thermally triggered valve is installed under the floor and in which the discharge orifice leads to the surface of the vehicle away from the floor.
8. Vehicle according to one of Claims 1 to 7, comprising a fuel cell, the said tank being used to store gaseous hydrogen.
9. Valve that remains open as soon as it is subjected for a first time to an increase in temperature, the valve comprising a triggering mechanism that uses a triggering member made of a shape memory alloy of characteristics such that it displays a first shape at ambient temperature and, when subjected for a first time to an increase in temperature that raises it above a predefined temperature threshold, it adopts a memorized shape different from the first shape and adopts it thermally and irreversibly.
10. Valve according to Claim 9, comprising a ball (53) cooperating with a seat (52) and a spring (59) pushing the ball back against its seat in order to keep the valve in the normally closed position at ambient temperature, and in which the triggering member is essentially a shape memory alloy pellet (7), the triggering mechanism further comprising a piston (57) inserted between the ball and the pellet, the piston pushing the ball away from its seat when the pellet switches from the first shape to the memorized shape, under the effect of a thrust exerted by the shape memory alloy pallet.

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